Solid-state nanopores are among a class of devices capable of biological analysis at the single-molecule level. To this point, a limited number of reliable nanopore formation methods have been reported. The two most widely used techniques are sculpting with a low energy ion beam and sputtering with a transmission electron microscope (TEM). In the former method, an ion sputtering system is used to controllably close a preformed opening of initial diameter of about 100 nm in a substrate. Using a feedback system capable of accurately detecting transmitted ion flux, single nanopores have been produced according to this technique with diameters as low as 1-2 nm. In the latter method, the tightly focused beam of a TEM is used to locally ablate a thin, free-standing solid-state membrane resulting in the formation of an individual nanopore. Subsequent exposure with a beam of reduced energy is then used to fluidize the membrane, slowly closing the initially formed pore with single nanometer precision.
The dimensional control and advantages offered by these fabrication techniques, however, is largely offset by slow membrane processing times leading to limited throughput. In both the low energy ion beam and TEM techniques, for example, only a single substrate or membrane can be processed at one time. Furthermore, nanopore backfill/shrinking processes can require several minutes to over an hour for completion. In view of these temporal processing disadvantages, large scale production of nanopore analytical devices remains unrealized.